SOIL CARBON-DIOXIDE CONCENTRATIONS AND CLIMATE IN A HUMID SUBTROPICAL ENVIRONMENT

Soil carbon dioxide content, temperature, and moisture were measured biweekly for one year at Pigeon Mountain, GA. Levels of soil CO2 ranged from 0.04% to 2.4% and were highest during the growing season, lowest during the winter. Soil temperature correlated positively with soil CO2, accounting for 90% of CO2 variation. Soil moisture variations decreased CO2 concentration at times of high soil water content when CO2 was flushed downward, and also at times of low soil moisture content when CO2 production was inhibited. A predictive model of logistic form using 14-day means of daily actual evapotranspiration fit the data well (R2 = 0.83). The model also tested well against soil CO2 data acquired in the coastal plain at Rocky Point, NC. If actual evapotranspiration rates are known, the model permits estimation of soil CO2 without preliminary field work, and can be used for studies of karst denudation, which require soil CO2 data for seasonal and regional comparison of solution rates. © 1990 by Association of American Geographers.